NOTICE: The protocol defined herein is a Draft Standard of the XMPP Standards Foundation. Implementations are encouraged and the protocol is appropriate for deployment in production systems, but some changes to the protocol are possible before it becomes a Final Standard.

Data Forms (XEP-0004) [1] ("x:data") provides a simple and interoperable way to request and present information for both applications and humans. However, the simple nature of "x:data" requires the form interpreter at times to guess as to exactly what type of information is being requested or provided. This document builds upon "x:data" to provide this additional validation.

This document defines a new namespace, "http://jabber.org/protocol/xdata-validate". The root element for this namespace is <validate/>, and MUST be contained within a <field/> element (qualified by the 'jabber:x:data' namespace) for each Data Forms field that possesses additional validation information.

The simplest usage is to provide a more-granular datatype for a <field/> element used in Data Forms. To provide this datatype information, a <validate/> element is included whose 'datatype' attribute specifies the data type of any <value/> contained within the <field/> element:

In addition to datatypes, the validation method can also be provided. The method is specified via a child element. The validation methods defined in this document are:

<basic/> for validation only against the datatype itself

<open/> for open-ended validation against the datatype

<range/> for validation against a given min/max and the datatype

<regex/> for validation against a given regular expression and the datatype

If no validation method is specified, form processors MUST assume <basic/> validation. The <validate/> element SHOULD include one of the above validation method elements, and MUST NOT include more than one.

Any validation method applied to a field of type "list-multi", "list-single", or "text-multi" (other than <basic/>) MUST imply the same behavior as <open/>, with the additional constraints defined by that method.

For "list-single" or "list-multi", to indicate that the user may enter a custom value (matching the datatype constraints) or choose from the predefined values, the <validate/> element shall contain an <open/> child element:

The <open/> validation method applies to "text-multi" differently; it hints that each value for a "text-multi" field shall be validated separately. This effectively turns "text-multi" fields into an open-ended "list-multi", with no options and all values automatically selected.

For "list-multi", validation can indicate (via the <list-range/> element) that a minimum and maximum number of options should be selected and/or entered. This selection range MAY be combined with the other methods to provide more flexibility.

If an implementation does not understand the specified datatype, it MUST validate according to the default "xs:string" datatype. If an implementation does not understand the specified method, it MUST validate according to the <basic/> method.

While all elements associated with this document MUST be qualified by the 'http://jabber.org/protocol/xdata-validate' namespace, explicitly declaring the default namespace for each instance can be overly verbose. However, Jabber/XMPP implementations have historically been very lax regarding namespacing, thus requiring some careful use of prefixes.

The use of namespace prefixes is RECOMMENDED for large forms, to reduce the data size. To maintain the highest level of compatibility, implementations sending the form using prefixes SHOULD use the namespace prefix "xdv", and SHOULD declare the namespace prefix mapping in the ancestor <x xmlns='jabber:x:data'/> element:

While this document is compatible with the existing "x:data" definition, form providers SHOULD first determine support for it, using either Entity Capabilities (XEP-0115) [7] if presence-aware or Service Discovery (XEP-0030) [8]. This is especially important for limited-connection and/or limited-capabilities devices, such as cell phones.

Although primarily intended for validating form submission, validation MAY have an impact on display, and MAY be applied to data forms that are not submitted (e.g. 'result' type forms). The following table outlines which field types a particular validation method is or is not appropriate for, and how a display SHOULD interpret the validation methods if considered [9]:

Table 1: Validation Methods and Field Types

Validation Method

SHOULD be Allowed

SHOULD NOT be Allowed

Display Suggestions

basic

fixed

list-multi

list-single

text-multi

text-single

hidden

jid-multi

jid-single

Display the datatype appropriate to the locale

open

jid-multi

jid-single

list-multi

list-single

text-multi

text-single

hidden

Display the datatype appropriate to the locale. For "text-multi" treat each value as a discrete entry (e.g. a user-entered list). For "list-multi" or "list-single", allow user to add/remove entries to select.

range

text-single

hidden

jid-multi

list-multi

text-multi

Display the datatype appropriate to the locale. For "text-single", allow user to increment/decrement through possible values. For "text-multi" treat each value as a discrete entry (e.g. a user-entered list). For "list-multi" or "list-single", allow user to add/remove entries to select.

regex

text-single

hidden

jid-multi

list-multi

text-multi

Display the datatype appropriate to the locale. If possible, display a valid example. For "text-multi" treat each value as a discrete entry (e.g. a user-entered list). For "list-multi" or "list-single", allow user to add/remove entries to select.

In order to submit new values to this registry, the registrant shall define an XML fragment of the following form and either include it in the relevant XMPP Extension Protocol or send it to the email address <registrar@xmpp.org>:

The XMPP Registrar maintains a registry of datatypes used in the context of Data Forms Validation (see <https://xmpp.org/registrar/xdv-datatypes.html>), where each datatype name includes the relevant prefix (e.g., "xs:anyURI").

In order to submit new values to this registry, the registrant shall define an XML fragment of the following form and either include it in the relevant XMPP Extension Protocol or send it to the email address <registrar@xmpp.org>:

<datatype>
<name>the full datatype name (e.g., "xs:string")</name>
<desc>a natural-language description of the datatype</desc>
<methods>the validation methods that may apply to the datatype</methods>
<min>the minimum value for the datatype (if any)</min>
<max>the maximum value for the datatype (if any)</max>
</datatype>

The registrant may register more than one datatype at a time, each contained in a separate <datatype/> element.

The following submission contains the built-in datatypes defined in XML Schema Part 2 that are deemed mostly like to be useful in the context of the Data Forms protocol; additional datatypes defined therein, as well as other datatypes not defined in XML Schema Part 2, may be registered via separate submissions in the future.

Matthew Miller

Appendix C: Legal Notices

Copyright

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Appendix G: Notes

3. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.

9. If a particular field type is not listed, the display MAY include validation support, but is not expected to do so.

10. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

Version 0.6 (2004-07-23)

Replaced <text-list/> with specific interpretations for other validation methods; Further clarified use of validation methods (other than "basic") with "list-single", "list-multi", and "text-multi"; Fixed errors in some examples; initial datatype registrations. (lw/psa)